Excavation construction method of large-section underwater tunnel with in-situ partition reservation in soft and broken surrounding rock

Abstract

The present invention provides an excavation construction method for an underwater tunnel with a medium-large cross-section in soft and broken surrounding rock with an in-situ partition reserved for the surrounding rock, comprising: S1, excavation section design; S2, advance drilling; S3, water blocking grouting; S4, synchronous excavation of a left pilot pit and a right pilot pit; S5, interval excavation of the partition surrounding rock; S6, excavation of a lower bench; S7, pouring of a secondary lining; and S8, performing a cyclic construction according to steps S3-S7, controlling the synchronous excavation advance of the left and right pilot pits to lead the excavation of the partition surrounding rock by 5-8 meters, controlling the excavation advance of the partition surrounding rock to lead the excavation of the lower bench by 8-12 meters, and controlling the secondary lining advance to be 8-10 meters from the tunnel face of the lower bench. Aiming at the characteristics of underwater tunnel projects in soft surrounding rocks, the present invention utilizes the in-situ reserved rock and soil between the upper left pilot pit and the upper right pilot pit to form a partition surrounding rock, excavates the left and right pilot pits simultaneously, and combines the excavation with the interval of the partition surrounding rock. This not only causes little disturbance to the surrounding rock, but also significantly shortens the construction period, while meeting the safety and economic requirements of the project.

Description

Technical Field

[0001] The invention relates to an excavation construction method for a large-section underwater tunnel in soft and broken surrounding rock with in-situ partition reservation in the surrounding rock, belonging to the technical field of tunnel construction. Background Art

[0002] When constructing large-cross-section underwater tunnels, staged excavation methods such as CD, stepping, CRD, and double-sidewall pilot tunneling are commonly employed. These methods primarily reduce large cross-sections to smaller ones, reducing the span of a single tunnel excavation to improve the stability and safety of tunnel construction. However, underwater tunnel excavation also faces engineering challenges such as poor surrounding rock stability, significant blasting disturbance, and unlimited groundwater recharge. When performing staged excavation of large-cross-section underwater tunnels in soft, fractured surrounding rock, excessive excavation can exacerbate surrounding rock disturbance, and the need for each section to be excavated in a strict sequential order significantly increases the construction period, making it difficult to meet project economic requirements. Summary of the Invention

[0003] In view of the above problems, the purpose of the present invention is to provide an excavation construction method for large-section underwater tunnel surrounding rock in soft and broken surrounding rock with in-situ reserved middle partition. According to the characteristics of underwater tunnel engineering in soft surrounding rock, the method utilizes the in-situ reserved rock and soil between the upper left pilot pit and the upper right pilot pit to form a middle partition surrounding rock, and excavates the left pilot pit and the right pilot pit simultaneously, and combines the excavation of the middle partition surrounding rock. It not only causes little disturbance to the surrounding rock, but also can greatly shorten the construction period, while meeting the safety and economic requirements of the project.

[0004] The present invention is achieved through the following technical solutions.

[0005] A method for excavating a large-section underwater tunnel in soft and broken surrounding rock with in-situ partition reservation is characterized by comprising the following steps:

[0006] S1. Excavation section design

[0007] The excavation section is divided into upper and lower steps, and the upper step is divided from left to right into the upper left pilot pit, the middle partition surrounding rock and the upper right pilot pit:

[0008] S2. Advance Drilling

[0009] Use the long and short drill rods of the anchor drilling rig to conduct advance drilling behind the tunnel face;

[0010] S3, water blocking grouting

[0011] Select an appropriate water plugging grouting method based on the results of the advance drilling in step S2;

[0012] S4. Simultaneous excavation of left and right pilot pits

[0013] First, advance support for the upper left pilot pit and the upper right pilot pit are simultaneously implemented. Then, the side wall rock mass of the upper left pilot pit and the side wall rock mass of the upper right pilot pit are simultaneously excavated to reserve the rock and soil between the upper left pilot pit and the upper right pilot pit in situ to form a partition surrounding rock. Then, initial support for the left wall and the right wall is implemented, and temporary support for the partition surrounding rock is implemented on both sides of the partition surrounding rock.

[0014] When constructing the initial support of the left and right walls, mortar anchor rods on the surrounding rock are inserted upwards obliquely on the left and right sides of the top of the middle septum surrounding rock, and the lower ends of the mortar anchor rods on the left and right sides are connected to the initial support of the left and right walls respectively, while the higher ends of the two are staggered along the tunnel direction. When constructing the temporary support of the middle septum surrounding rock, mortar anchor rods on the lower side of the surrounding rock are inserted upwards obliquely on both sides of the middle septum surrounding rock at certain intervals along the direction of the tunnel, so that the middle septum surrounding rock forms an alternating distribution of the middle septum surrounding rock reinforcement area and the middle septum surrounding rock non-reinforcement area.

[0015] S5, Excavation with intervals between surrounding rocks

[0016] First, the temporary support of the septum surrounding rock in the non-reinforced area of ​​the septum surrounding rock is removed, and then the non-reinforced area of ​​the septum surrounding rock is excavated. Then, the initial support of the non-reinforced area of ​​the septum surrounding rock is constructed on the top of each non-reinforced area of ​​the septum surrounding rock, and the initial support of the non-reinforced area of ​​the septum surrounding rock is connected with the initial support of the left wall and the initial support of the right wall on both sides to form a whole. Then, the temporary support of the septum surrounding rock in the reinforced area of ​​the septum surrounding rock is removed, and then the reinforced area of ​​the septum surrounding rock is excavated. Then, the initial support of the reinforced area of ​​the septum surrounding rock is constructed on the top of each reinforced area of ​​the septum surrounding rock, and the initial support of the reinforced area of ​​the septum surrounding rock is connected with the initial support of the left wall and the initial support of the right wall on both sides and the initial support of the non-reinforced area of ​​the septum surrounding rock to form a whole.

[0017] S6, excavation of lower steps

[0018] First, advance support is applied to the lower step, then the rock mass of the lower step is excavated, and finally, initial support is applied to the lower step to close the ring.

[0019] S7, pouring secondary lining;

[0020] S8. Carry out circular construction according to steps S3-S7, control the synchronous excavation progress of the left pilot pit and the right pilot pit to be 5-8m ahead of the excavation of the middle partition surrounding rock, control the excavation progress of the middle partition surrounding rock to be 8-12m ahead of the excavation of the lower bench, and control the secondary lining progress to be 8-10m away from the lower bench face.

[0021] Preferably, in step S2, a total of 6 water exploration holes are drilled each time, and the outer deviation angle of the drilling hole is 10°.

[0022] Preferably, in step S3, according to the water gushing amount of the water exploration hole in the advance drilling result of step S2, full-section water blocking, local grouting water blocking or no water blocking is adopted.

[0023] Preferably, when 4 or more of the water exploration holes are full of water and the total water volume is greater than 15m 3 / h, full-section surface water blocking grouting is used; when the total water volume is less than 15m 3 / h but the water output of some holes is greater than 3m 3 / h, local water blocking grouting is used; when the water output of the six holes is less than 3m 3 / h and the total water output is less than 15m 3 / h, grouting is not used to block water, and the next construction step is directly entered.

[0024] Preferably, the width of the connection between the bottom of the middle partition surrounding rock and the lower step is 1.2 to 1.8 m.

[0025] Preferably, in steps S4, S5 and S6, a cantilever-type tunnel boring machine is used to excavate the rock mass.

[0026] Preferably, in steps S4, S5 and S6, the initial support is constructed by combining steel arches, shotcrete and mortar anchors.

[0027] Preferably, in steps S4 and S6, the advanced support is constructed by combining advanced small-duct grouting and advanced pipe-roof construction.

[0028] Preferably, the advanced small conduit grouting adopts a double layer of φ42mm×4mm advanced small conduit, L=4.5m, annular longitudinal spacing of 0.4×3m, the first layer external insertion angle of 5°~15°, the second layer external insertion angle of 40°~45°, and a plum blossom shape arrangement.

[0029] Preferably, in step S4, the temporary support of the surrounding rock is constructed by combining temporary steel arches, steel mesh and shotcrete.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention uses advance drilling and selects a suitable grouting and water blocking method based on the exploration results of the advance drilling, which can effectively intercept water sources, reduce or eliminate tunnel water inflow, and ensure subsequent construction safety.

[0032] (2) The present invention utilizes the in-situ reserved rock and soil between the upper left pilot pit and the upper right pilot pit to form a partition surrounding rock. Without the need to construct additional supporting reinforcement facilities such as a partition wall, the present invention can reduce the span of a single tunnel excavation and weaken the disturbance between the upper left pilot pit and the upper right pilot pit during excavation through the supporting and isolating effect of the in-situ reserved partition surrounding rock, thereby enabling the left pilot pit and the right pilot pit to achieve efficient and safe synchronous excavation construction, thereby greatly shortening the construction period.

[0033] (3) The present invention staggers and obliquely inserts the upper mortar anchor rods of the surrounding rock upward along the tunnel direction on the left and right sides of the top of the middle septum surrounding rock, and obliquely inserts the lower mortar anchor rods of the surrounding rock upward at certain intervals on both sides of the middle septum surrounding rock, so that the middle septum surrounding rock forms an alternating distribution of the middle septum surrounding rock reinforcement area and the middle septum surrounding rock non-reinforcement area. Firstly, the supporting stability of the middle septum surrounding rock can be ensured, and secondly, the interval excavation of the middle septum surrounding rock can be realized, thereby reducing the disturbance to the nearby surrounding rock during the excavation of the middle septum surrounding rock, so as to ensure the safety of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a front view of the excavation construction method of the present invention;

[0035] Figure 2 for Figure 1 Cross-section at AA in the middle;

[0036] Figure 3 for Figure 2 Cross-section at the middle BB;

[0037] Figure 4 This is a schematic diagram of the process of excavation between surrounding rock intervals;

[0038] Figure 5 It is a front view of the water blocking grouting in the present invention;

[0039] Figure 6 It is a cross-sectional view of the water blocking grouting in the present invention;

[0040] The meanings of the symbols in the above figure are: upper step 1, upper left pilot tunnel 101, upper right pilot tunnel 102, middle septum surrounding rock 103, middle septum surrounding rock reinforcement area 1031, middle septum surrounding rock non-reinforced area 1032, lower step 2, middle septum surrounding rock temporary support 3, upper left pilot tunnel advance support 4, left side wall initial support 5, water exploration hole 6, upper right pilot tunnel advance support 7, right side wall initial support 8, tunnel face 9, upper mortar anchor rods for surrounding rock 10, lower mortar anchor rods for surrounding rock 11, middle septum surrounding rock non-reinforced area initial support 12, middle septum surrounding rock reinforcement area initial support 13, lower step advance support 14, lower step initial support 15, secondary lining 16. DETAILED DESCRIPTION

[0041] The present invention will be further described below in the form of specific embodiments in conjunction with the accompanying drawings. It should be noted that the following embodiments are merely illustrative of the present invention in the form of examples, but the scope of protection of the present invention is not limited thereto. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] This embodiment provides a method for excavating a large-section underwater tunnel in soft and broken surrounding rock with an in-situ partition. Figures 1 to 6 , which includes the following steps:

[0043] S1. Excavation section design

[0044] The excavation section is divided into upper bench 1 and lower bench 2. The upper bench 1 is divided from left to right into upper left pilot tunnel 101, middle partition surrounding rock 103 and upper right pilot tunnel 102:

[0045] S2. Advance Drilling

[0046] See also Figure 5 and Figure 6 , using the long and short drill rods of the anchor drilling rig to conduct advance drilling behind the tunnel face. Each drilling is done with 6 water exploration holes, with an external deviation angle of 10 degrees. The water exploration holes can also be used as drainage holes to reduce the impact of water pressure on the surrounding rock.

[0047] S3, water blocking grouting

[0048] See also Figure 5 and Figure 6 According to the water gushing amount of the water exploration holes in the advance drilling results of step S2, full-section water blocking, local grouting water blocking or no water blocking is adopted. Specifically: when 4 or more water exploration holes are full of water and the total water volume is greater than 15m 3 / h, full-section water blocking grouting is used; when the total water volume is less than 15m 3 / h but the water output of some holes is greater than 3m 3 / h, adopt local water blocking grouting; when the water output of 6 holes is less than 3m 3 / h and the total water output is less than 15m 3 / h, do not use water blocking grouting, and directly proceed to the next construction step;

[0049] The grouting range of water blocking grouting is: within the water outlet channel, 5 to 6 meters outside the outer contour line of the tunnel excavation, the effective diffusion radius of single hole grouting is R = 3.6 meters, and the final pressure after grouting is 2 to 3 times the net water pressure; after grouting, the total water output is less than 2m 3 / h and the water output at one place is less than 0.6m 3 / h, then the grouting is finished;

[0050] S4. Simultaneous excavation of left and right pilot pits

[0051] See also Figures 1 to 3First, the upper left pilot tunnel advance support 4 and the upper right pilot tunnel advance support 7 are synchronously constructed. Then, the STR318H cantilever tunnel boring machine is used to synchronously excavate the side wall rock mass of the upper left pilot tunnel 101 and the side wall rock mass of the upper right pilot tunnel 102, so that the rock and soil between the upper left pilot tunnel 101 and the upper right pilot tunnel 102 are reserved in situ to form the middle surrounding rock 103, and the width of the connection between the bottom of the middle surrounding rock 103 and the lower step 2 is controlled to be 1.2 to 1.8 meters; then, the left side wall initial support 5 and the right side wall initial support 8 are constructed, and the middle surrounding rock temporary support 3 is constructed on both sides of the middle surrounding rock 103;

[0052] When constructing the left side wall initial support 5 and the right side wall initial support 8, the upper mortar anchor rods 10 of the surrounding rock are obliquely inserted upward on the left and right sides of the top of the middle septum surrounding rock 103, and the lower ends of the said mortar anchor rods 10 of the surrounding rock top on the left and right sides are respectively connected to the left side wall initial support 5 and the right side wall initial support 8, while the higher ends of the two are staggered and connected along the tunnel direction; when constructing the middle septum surrounding rock temporary support 3, the lower mortar anchor rods 11 of the surrounding rock are obliquely inserted upward on both sides of the middle septum surrounding rock 103 at certain intervals along the tunnel direction, so that the middle septum surrounding rock 103 forms an alternating middle septum surrounding rock reinforcement area 1031 and a middle septum surrounding rock non-reinforcement area 1032;

[0053] S5, Excavation with intervals between surrounding rocks

[0054] See also Figure 4 First, the temporary support 9 for the septum surrounding rock in the non-reinforced area 1032 of the septum surrounding rock is removed, and then the non-reinforced area 1032 of the septum surrounding rock is excavated. Then, the initial support 12 for the non-reinforced area of ​​the septum surrounding rock is constructed on the top of each non-reinforced area 1032 of the septum surrounding rock, and the initial support 12 for the non-reinforced area of ​​the septum surrounding rock is connected with the initial support 5 for the left wall and the initial support 8 for the right wall on both sides to form a whole. Then, the temporary support 9 for the septum surrounding rock in the reinforced area 1031 of the septum surrounding rock is removed, and then the reinforced area 1031 of the septum surrounding rock is excavated. Then, the initial support 13 for the reinforced area of ​​the septum surrounding rock is constructed on the top of each reinforced area 1031 of the septum surrounding rock, and the initial support 13 for the reinforced area of ​​the septum surrounding rock is connected with the initial support 5 for the left wall and the initial support 8 for the right wall on both sides and the initial support 12 for the non-reinforced area of ​​the septum surrounding rock to form a whole.

[0055] S6, excavation of lower steps

[0056] First, the lower bench advance support 14 is applied, then the rock mass of the lower bench 2 is excavated, and finally the lower bench initial support 15 is applied to close the ring;

[0057] S7, pouring secondary lining;

[0058] S8. Carry out circular construction according to steps S3-S7, controlling the synchronous excavation of the left and right pilot pits to be 5-8 m ahead of the excavation of the middle partition surrounding rock, controlling the excavation of the middle partition surrounding rock to be 8-12 m ahead of the excavation of the lower bench, and controlling the distance between the secondary lining and the tunnel face of the lower bench to be 8-10 m.

[0059] In the above steps, the temporary support 3 of the surrounding rock is constructed by combining temporary steel arches, steel mesh and shotcrete;

[0060] In the above steps, the initial supports for the left wall 5, the right wall 8, the middle septum surrounding rock reinforcement area 13, the middle septum surrounding rock non-reinforcement area 12, and the lower step 15 are constructed using a combination of steel arches, shotcrete, advance small pipes, and mortar anchors; wherein the advance small pipes have a length of 3-4.5 m and the mortar anchors have a length of 3.5-4.5 m.

[0061] In the above steps, the upper left pilot tunnel advance support 4, the upper right pilot tunnel advance support 7 and the lower step advance support 14 are constructed by combining advance small conduit grouting and advance pipe scaffolding; among them, the advance small conduit grouting adopts a double-layer φ42mm×4mm advance small conduit, L=4.5m, annular longitudinal spacing of 0.4×3m, the first layer external insertion angle of 5°~15°, the second layer external insertion angle of 40°~45°, and a plum blossom arrangement.

Claims

1. A method for excavating a large-section underwater tunnel in soft and broken surrounding rock with in-situ partition reservation, characterized in that: The steps include: S1. Excavation section design The excavation section is divided into an upper step (1) and a lower step (2), and the upper step (1) is divided from left to right into an upper left pilot pit (101), a middle partition surrounding rock (103) and an upper right pilot pit (102): S2. Advance Drilling Use the long and short drill rods of the anchor drilling rig to conduct advance drilling behind the tunnel face; S3, water blocking grouting Select an appropriate water plugging grouting method based on the results of the advance drilling in step S2; S4. Simultaneous excavation of left and right pilot pits First, the upper left pilot pit advance support (4) and the upper right pilot pit advance support (7) are synchronously implemented, and then the side wall rock mass of the upper left pilot pit (101) and the side wall rock mass of the upper right pilot pit (102) are synchronously excavated, so that the rock and soil between the upper left pilot pit (101) and the upper right pilot pit (102) are reserved in situ to form a middle septum surrounding rock (103), and then the left side wall initial support (5) and the right side wall initial support (8) are implemented, and the middle septum surrounding rock temporary support (3) is implemented on both sides of the middle septum surrounding rock (103); When constructing the left side wall initial support (5) and the right side wall initial support (8), the upper mortar anchor rods (10) of the surrounding rock are inserted obliquely upwards on the left and right sides of the top of the middle septum surrounding rock (103), and the lower ends of the said mortar anchor rods (10) of the surrounding rock top on the left and right sides are respectively connected to the left side wall initial support (5) and the right side wall initial support (8), while the higher ends of the two are staggered along the tunnel direction; when constructing the middle septum surrounding rock temporary support (3), the lower mortar anchor rods (11) of the surrounding rock are inserted obliquely upwards on both sides of the middle septum surrounding rock (103) at a certain interval along the tunnel direction, so that the middle septum surrounding rock (103) forms an alternating middle septum surrounding rock reinforcement area (1031) and a middle septum surrounding rock non-reinforcement area (1032); S5, Excavation with intervals between surrounding rocks First, the temporary support (3) of the middle septum surrounding rock non-reinforced area (1032) is removed, and then the middle septum surrounding rock non-reinforced area (1032) is excavated. Then, the initial support (12) of the middle septum surrounding rock non-reinforced area is constructed on the top of each middle septum surrounding rock non-reinforced area (1032), and the initial support (12) of the middle septum surrounding rock non-reinforced area is connected with the initial support (5) of the left wall and the initial support (8) of the right wall on both sides to form a whole. Then, the middle septum surrounding rock is removed. The intermediate surrounding rock reinforcement area (1031) is partially provided with temporary support (3) for the intermediate surrounding rock reinforcement area, and then the intermediate surrounding rock reinforcement area (1031) is excavated, and then the intermediate surrounding rock reinforcement area initial support (13) is constructed on the top of each intermediate surrounding rock reinforcement area (1031), and the intermediate surrounding rock reinforcement area initial support (13) is connected with the left side wall initial support (5), the right side wall initial support (8) and the intermediate surrounding rock non-reinforcement area initial support (12) to form a whole; S6, excavation of lower steps First, the lower step advance support (14) is applied, then the rock mass of the lower step (2) is excavated, and finally the lower step initial support (15) is applied to close the ring; S7, pouring secondary lining; S8. Carry out circular construction according to steps S3-S7, control the synchronous excavation progress of the left pilot pit and the right pilot pit to be 5-8m ahead of the excavation of the middle partition surrounding rock, control the excavation progress of the middle partition surrounding rock to be 8-12m ahead of the excavation of the lower bench, and control the secondary lining progress to be 8-10m away from the lower bench face.

2. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 1 is characterized in that: In the step S2, a total of 6 water exploration holes (6) are drilled each time, and the outer deviation angle of the drilling hole is 10°.

3. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 2 is characterized in that: In step S3, according to the water gushing amount of the water exploration hole in the advance drilling result of step S2, full-section water blocking, local grouting water blocking or no water blocking is adopted.

4. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 3 is characterized in that: When 4 or more water holes are full of water and the total water volume is greater than 15m 3 / h, full-section water blocking grouting is used; when the total water volume is less than 15m 3 / h but the water output of some holes is greater than 3m 3 / h, adopt local water blocking grouting; when the water output of 6 holes is less than 3m 3 / h and the total water output is less than 15m 3 / h, grouting is not used to block water, and the next construction step is directly entered.

5. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 1 is characterized in that: The width of the connection between the bottom of the middle partition surrounding rock (103) and the lower step (2) is 1.2 to 1.8 m.

6. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 1 is characterized in that: In steps S4, S5 and S6, a cantilever-type tunnel boring machine is used to excavate the rock mass.

7. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 1 is characterized in that: In steps S4, S5 and S6, the initial support is constructed by combining steel arches, shotcrete and mortar anchors.

8. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 1 is characterized in that: In the steps S4 and S6, the advanced support is constructed by combining advanced small-duct grouting and advanced pipe-roof.

9. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 8 is characterized in that: The advanced small pipe grouting adopts a double layer of φ42mm×4mm advanced small pipe, L=4.5m, the longitudinal spacing of the ring is 0.4×3m, the first layer has an external insertion angle of 5°~15°, the second layer has an external insertion angle of 40°~45°, and is arranged in a plum blossom shape.

10. The excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in weak and broken surrounding rock according to claim 1 is characterized in that: In step S4, the temporary support of the surrounding rock is constructed by combining temporary steel arches, steel mesh and shotcrete.

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